1. Technical Field
The present invention relates to a circuit device, an electronic apparatus, and the like.
2. Related Art
A method of performing PWM control of transistors in an H bridge circuit is known as a method for controlling the torque of a motor. With this method, a charge period in which the output current of the H bridge circuit increases and a decay period in which the output current of the H bridge circuit decreases are repeated, and the driving current for the motor is controlled by controlling the lengths of the periods.
In the case of performing this kind of control, a malfunction detection circuit is provided in order to protect the motor and the H bridge from malfunctions caused by excess current. For example, JP-A-2007-74794 discloses a technique in which a first sense resistor is provided on the power supply side of an H bridge and a second sense resistor is provided on the ground side of the H bridge, and excess current is detected by detecting the voltage between both ends of the first sense resistor and the voltage between both ends of the second sense resistor.
In JP-A-2007-74794, an increase in the voltage between both ends of the sense resistor in the case where excess current flows in the sense resistor is detected as a malfunction. However, if a current path other than the sense resistor is generated, excess current can no longer be correctly detected. For example, in the case of breakdown of the junction between the drain of the transistor in the H bridge and the substrate due to excess voltage, part of the excess current will flow in the substrate, and the voltage increase in the sense resistor will be smaller.
Thus, the method of detecting a voltage increase when excess current flows in a resistor is problematic in that in the case of breakdown of a transistor, excess current that flows due to the breakdown of the transistor cannot be detected as a malfunction.
According to some aspects of the invention, it is possible to provide a circuit device, an electronic apparatus, and the like, according to which it is possible to detect excess current caused by breakdown of a transistor.